The present invention relates to a tree harvesting machine and more particularly to a control system to be used in a tree harvesting machine of the type disclosed in U.S. Pat. No. 3,833,034 granted to Menzel et al on Sept. 3, 1974, and having the same assignee as the present application.
The tree harvesting machine disclosed in the above-identified patent includes a delimber assembly having openable and closable delimber knives and a feed assembly having openable, closable and rotatable feed rolls. A boom located on the machine includes a felling head which severs a tree which is then positioned by the boom in the delimber and feed assemblies in a delimbing position. The delimber and feed assemblies include solenoids which actuate valving for controlling hydraulic cylinders to position the delimber knives and feed rolls through solenoid actuated valving and hydraulic cylinders, and include solenoids which actuate valving for controlling hydraulically operable clutch and reversing means in the feed roll drive transmission to selectively effect forward and reverse driving of the feed rolls.
In the past, only manual, individual control of the valves, clutch, and the transmission were possible which required the operator's attention at the delimber and feed assemblies during the delimbing cycle. The operator was not free to select or cut other trees while the delimbing cycle was in operation and this reduced the cycle time and hence the cost effectiveness of the entire machine. Further, the sequencing of the delimbing cycle was controlled manually for each cycle rather than being automatically selectable which further reduced the cycle time.
Further, past systems relied on limit switches or proximity sensors to initiate different portions of the cycle. A system of this sort is disclosed in the U.S. Pat. No. 3,586,078 granted to Hamilton on June 22, 1971. The disadvantage of this system is the remote wiring and additional switching required as compared to a time cycled system.